Hair loss or alopecia may result from genetic factors, aging, local or systemic disease or certain therapeutic drugs designed to alleviate conditions such as cancer. Various preparations for preventing or reducing hair loss and/or promoting hair growth are proposed, for example those containing female hormones which can promote blood circulation, reinforce hair root function, moisturize scalp and inhibit male hormone function; 5α-reductase inhibitors; or minoxdil, trichosaccharides or the like as main ingredients. However, they cannot show satisfactory hair growth-promoting effects, and some may raise side-effect problems such as sexual function disorder.
It is strongly desired to develop a hair growth-promoting agent having superior effects without side effect.
Prostaglandins (hereinafter, referred to as PG(s)) are members of class of organic carboxylic acids, which are contained in tissues or organs of human or other mammals, and exhibit a wide range of physiological activity. PGs found in nature (primary PGs) generally have a prostanoic acid skeleton as shown in the formula (A):

On the other hand, some of synthetic analogues of primary PGs have modified skeletons. The primary PGs are classified to PGAs, PGBs, PGCs, PGDs, PGEs, PGFs, PGGs, PGHs, PGIs and PGJs according to the structure of the five-membered ring moiety, and further classified into the following three types by the number and position of the unsaturated bond at the carbon chain moiety:
Subscript 1: 13,14-unsaturated-15-OH
Subscript 2: 5,6- and 13,14-diunsaturated-15-OH
Subscript 3: 5,6-, 13,14-, and 17,18-triunsaturated-15-OH.
Further, the PGFs are classified, according to the configuration of the hydroxyl group at the 9- and 11-position, into α type (the hydroxyl group is of an α-configuration) and β type (the hydroxyl group is of β-configuration).
Certain prostaglandin compound having two hetero atoms at the 15 position are known in the art. U.S. Pat. No. 4,088,775 discloses certain 15-ethylenedioxy-prostanoic acid. In addition, U.S. Pat. No. 4,870,104 discloses 11 halo prostaglandins which may have an ethylenedioxymethylene group at 15-position and use thereof as agents inhibiting gastric acid secretion. Further, U.S. Pat. No. 6,353,014 discloses a certain 15-ketal analogs of F series prostaglandins useful for treating ocular hypertension and glaucoma.
Those prior arts do not disclose nor suggest that prostaglandin compound having two hetero atoms at the 15 position may be useful in the stimulation of hair growth.